I tell ya, astronomy is just one of those quicksand hobbies that you just can’t escape!
I have begun my journey in astronomical spectroscopy. I recently acquired a Shelyak ALPY 600 with guiding module. I was graced with a very clear night a few nights ago. The moon was almost full, but that didn’t bother me this time. The transparency and seeing were good. I wanted to take the spectra of a few bright stars to whet my stellar palate.
Configuring the ALPY 600 was pretty easy. I could focus the optical assembly easily during the day by pointing it at the sun. Focusing the guiding module was as simple as getting the slit in focus. I use my ASI183MC camera that I got for planetary imaging last summer as the science camera. Although a color camera is not ideal, its small pixels are over sampled enough to make it usable. The ASI178MM, my conventional imaging guiding camera, suffices for plate solving and guiding duties. I still use PHD2 for guiding, and I use Sharpcap to capture the data. For these stars, I captured 200 images each, with exposure times around a quarter to half a second.
For processing, I have decided to start with BASS. While daunting at first, the program was pretty easy to pick up. The calibration process was tricky. I began by taking a spectrum of a flourescent lamp, but this didn’t quite work out perfectly. I ended up using absorption lines in the star spectra to calibrate. I think I will need the calibration module available for the ALPY 600 to take calibration images for each target. It’s possible for the different angle of targets to cause droop in the spectrograph, so to get very accurate calibrations, you have to take calibration images in the same orientation in which the equipment is collecting data.
Aldebaran is a giant star around 65 light years away in Taurus. It is a cooler star at around 3,900 K, but it is 44 times the diameter of the Sun, making it 400 times more luminous. Its spectral type is K5+ III.
Alnitak, a familiar star in Orion’s belt, is actually a triple star system. The primary star is a hot blue supergiant. Alnitak is around 1,260 light years away! The spectral types of the three constituent stars are O9.5Iab, B1IV, and B0III.
Bellatrix, Orion’s left shoulder, is considered a “standard star,” but has been shown to be variable. It’s 250 light years away and has a spectral type of B2 III.
Don’t say it thrice, Betelgeuse is everyone’s hope for a supernova in our lifetime. This red supergiant, Orion’s right shoulder, is so large that it’s apparent diameter is estimated to be only half that of the moons of Uranus, at around 0.05 arcseconds! It’s 550 light years away, and while it is about 17 times as massive as our Sun, it is possibly 1000 times the radius.
Capella is the brightest “star” in Auriga, although it is actually a system of four stars, two orbiting binary pairs. One binary system consists of two yellow giant stars, while the second binary pair, around 10,000 astronomical units away from the first, consists of red dwarfs. This system is about 43 light years away and is mainly of spectral type G1III.
Mirfak, the brightest star in Perseus, is circumpolar for those of us in the northern US. It is a member of the Alpha Persei Cluster, which is visible with binoculars. It’s 510 light years away and of spectral type F5 Ib.
Pollux, an evolved giant star only 34 light years away, is the brightest star in Gemini. A stable star, it’s used as a spectral reference. Spectral type is K0 III.
Procyon is the brightest member of Canis Minor and the eighth brightest star in the sky. A binary star system only 11 light years away, it consists of a main sequence star of spectral type F5 IV–V and a white dwarf of spectral type DQZ. The pair orbit each other every 40 years at a distance of 15 astronomical units.
If you’ve made it this far, you must really love stars. I have compiled all of these into a poster,
of which you can get prints on my Redbubble store.
